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EXHIBIT 55 STREAM CHANNEL PARAMETERS AND CHANGES DUE TO MINING-INDUCED SUBSIDENCE INTRODUCTION TO STUDY Wright Water Engineers, Inc. (WWE) and Emest Pemberton, P.E.', have determined the extent to which projected subsidence will impact stream channel stability and sediment transport at Mountain Coal Company's (MCC) West Elk Mine. The following text summarizes WWE's approach and findings. This discussion applies to both the Apache Rocks and the Box Canyon permit revision areas, herein referred to as the study areas. Figure 1 shows the drainage basins of 25 streams in the vicinity of the mining areas. Each basin has an identification number which will be used throughout this discussion of stream channel • parameters and subsequent changes. As shown in Figure 1, Basins 1 through 6 are located in the Dry Fork of Minnesota Creek (Dry Fork) drainage; Basins 7 through l~ comprise the Sylvester Gulch drainage; Basins 16 through 19 are direct tributaries to the North Fork of the Gunnison River (North Fork); and Basins 20 through ZS are tributaries to Raven Gulch. Table 1 identifies which streams may be impacted by the proposed mining. As shown in Table 1, the mine area will underlie portions of 16 separate minor tributaries of the North Fork and Dry' Fork in the study areas. A detailed discussion of the mine plan for these areas is given in Exhibit 60. The remaining 9 basins were determined to be outside the influence of mining activities. The first portion of this hydraulic and hydrologic evaluation establishes pre-mining, or baseline. conditions. The second portion of this evaluation describes the potential and likely impacts of mining operations on the surface drainage system and channel chazacteristics. 'Adjunct Scientist with WWE, Former Head of Sedimentation and River Hydraulics Section, H}•drolog}• • Department, Chief Engineer and Assistant Commissioner's Office. U.S. Bureau of Reclamation.